1. Field of the Invention
The present invention relates generally to electrophotography, more particularly to color, hard copy printing and plotting, and, more specifically, to a liquid toner developer actuation system for a color hard copy apparatus.
2. Description of the Related Art
In electrophotographic printing an electrostatic latent image in a photoconductor is developed by applying toner to the latent image. Contact of the toner developed image with paper transfers the toner to the paper to create a hard copy reproduction of the image. In further detail, a charge is applied to a photoconductive insulating surface area of a photoconductor. The surface area is exposed to a pattern of light. By this exposure a latent image of the pattern is formed in the charged photoconductor surface. The latent image is then developed by the application of electroscopic toner to the photoconductive material. The toner of the developed image is transferred by contact to a hard copy sheet, usually a paper medium and fused, or fixed, thereto. The photoconductor surface is then cleaned removing the image and reused for the next image. This basic construct is used in a variety of state of the art products such as computer printers and plotters, copiers, facsimile machines, and the like.
In the field of color hard copy reproduction, such as by laser printers using liquid electrophotography (LEP) techniques, the use of color liquid toners (generally yellow, magenta, cyan (the subtractive primary colors), and black) present challenging implementation problems. One such problem is in the developer mechanism of the hard copy apparatus where color toner is transferred from a reservoir in a developer mechanism or module, to a photoconductor, in order to develop the latent image. After a photosensitized material is exposed to a pattern of illumination, a latent image of that pattern exists in the distribution of dissipated electrical charges on the surface of the material. The electrostatic latent image is developed by the attraction of toner to the latent image at the developer module (of a type dependent upon the type of toner employed, liquid or dry powder; e.g., air nozzles, brushes, rollers, or the like).
In a development cycle as practiced in the prior art, the development module is brought into toner transfer position with the photoconductor in order to initiate the image development process. This involves moving the developer assembly into contact with the photoconductor at the location of the latent image. Since the entire mass of the developer assembly must be moved, this requires a motor and precision guidance hardware. In addition, if any parts of the developer assembly are driven from a common gear train then the gear train must allow for this motion. Further there is no simple mechanism to vary the time duration of developer assembly proximity with the photoconductor for developing the latent image. This adds additional complexity and cost to the developer design.
Therefore, there is a need for an improved, low cost, latent image developer actuation system for hard copy producing machines.